In circuits such as switching power supplies and inverters, semiconductor elements such as switching elements and diodes are used. These semiconductor elements are required to have high breakdown voltage and low on-resistance. The relationship between breakdown voltage and on-resistance is a trade-off relationship that depends on element materials.
As technologies have advanced, semiconductor elements now have low on-resistance close to the limit for silicon, which is a principal element material. So as to further increase breakdown voltage or further reduce on-resistance, element materials need to be changed. If GaN-based semiconductors such as GaN and AlGaN are used as switching element materials, the trade-off relationship depending on materials can be improved and dramatically high breakdown voltage and low on-resistance can be achieved.
However, if a high drain voltage is applied to a switching element using a GaN-based semiconductor, a problem called “current collapse” that causes an increase in on-resistance occurs.